T4 templates error: loading the include file ef.utility.cs.ttinclude returned a null or empty string

Question

I have overridden the controller generation T4 templates (ControllerWithContext.tt) as described here.
I would like to take advantage of the code helper utilities found in EF.utility.CS.ttinclude as used in the POCO model generator T4 template. Therefore I copied the following lines from my Model.tt to my ControllerWithContext.tt.

<#@ include file="EF.Utility.CS.ttinclude"#>

However, when I try to add a controller I am getting the error message

Loading the include file 'EF.utility.CS.ttinclude' returned a null or empty string

According to the MSDN documentation, this error is because the included file is blank, which it clearly isn't because it works with Model.tt

The only difference I can see is that the overridden ControllerWithContext.tt does not have a Custom Tool defined, whereas the Model.tt has it set to TextTemplatingFileGenerator.

My workaround is to copy the functions I need from ef.utility.cs.ttinclude into my ControllerWithContext.tt, which in itself threw up more errors but which were easily solved.

How can I include T4 templates without a custom tool defined?

Answer 1

Following @DustinDavis' advice, and using the invaluable information found on OlegSych's site, here's what I did:

• Created a new project called CodeGenerationTools.

• Added project references to

  • System.Data.Entity.Design
  • EnvDTE
  • System.Data.Entity
  • Microsoft.VisualStudio.TextTemplating.10.0

  For this last reference I had to install the correct version of the Visual Studio SDK

• Copied the EF.Utility.CS.ttinclude file into the project.
• Renamed it CodeGenerationTools.cs
• Edited the file and convert all <#@ import namespace="<name>" #> to using <name>;
• Deleted the opening and closing <#+ #>
• Added the directive using Microsoft.VisualStudio.TextTemplating;

• Extended the class:

  public class CodeGenerationTools : TextTransformation
  

• Override the TransformText method

  public override string TransformText() {
      throw new NotImplementedException();
  }
  

• Added empty constructor

  public CodeGenerationTools() {
      _textTransformation = DynamicTextTransformation.Create(this);
      _code = new CSharpCodeProvider();
      _ef = new MetadataTools(_textTransformation);
      FullyQualifySystemTypes = false;
      CamelCaseFields = true;
  }
  

• Finally, build this project.

The next steps took place in the main project - Edited the T4 template file. - Changed template directive to

    <#@ template language="C#" HostSpecific="True" debug="false" inherits="CodeGenerationTools"#>

- Added the directives

    <#@ assembly name="C:\Visual Studio 2010\Projects\CodeGenerationTools\CodeGenerationTools\bin\Debug\CodeGenerationTools.dll" #>
    <#@ import namespace="CodeGenerationTools" #>

All of which now means I can use the helper methods found in EF.Utility.CS.ttinclude in my own T4 templates, and I have the means to add my own helper methods which will be available to all projects.

Answer 2

If you have Visual Studio 2012 or 2013, install this EF tool to resolve the error.